Rat gastroduodenal motility in vivo: interaction of GABA and VIP in control of spontaneous relaxations

• Published in: American journal of physiology: Gastrointestinal and liver physiology Vol. 275; no. 5; pp. G897 - G903
• Main Authors: Krantis, Anthony, Mattar, Kamal, Glasgow, Ian
• Format: Journal Article
• Language: English
• Published: United States 01.11.1998
• Subjects: nitric oxide; vasoactive intestinal peptide; γ-aminobutyric acidA
• ISSN: 0193-1857; 1522-1547
• DOI: 10.1152/ajpgi.1998.275.5.G897

Spontaneous relaxations occurring within motor activity in the rat gastroduodenum in vivo can be distinguished by their dependence on either nitric oxide (NO) or ATP. We examined the interaction of γ-aminobutyric acid (GABA) and vasoactive intestinal peptide (VIP) within pathways controlling this activity in the antrum (S) and duodenum (D) of anesthetized Sprague-Dawley rats, using miniaturized extraluminal foil strain gauges oriented perpendicular to (S , D ) or in the axis of (S ) the circular smooth muscle. The NO synthase inhibitor N -nitro-l-arginine methyl ester (l-NAME; 10 mg/kg iv) attenuated ( P < 0.05) antral relaxations and, in the duodenum, nonpropagating "intergroup" relaxations. The GABA receptor antagonist bicuculline (350 μg/kg sc) had similar effects. The GABA agonist 3-amino-1-propanesulfonic acid stimulatedl-NAME-sensitive relaxations at S and D . Propagating "grouped" responses were unchanged. VIP (6 μg/kg iv) always induced a relaxation of the duodenum, which was attenuated by bicuculline andl-NAME. VIP caused simultaneous responses at S and S ; however, the antrum displayed either contraction or relaxation in response to VIP. All antral relaxations in response to VIP were attenuated ( P < 0.05) byl-NAME; however, only VIP-induced relaxations at S were sensitive to bicuculline. VIP-induced contractions were also unaffected. GABA receptors mediate the pathway(s) controlling NO-related spontaneous relaxations of the antrum and duodenal circular muscle. All VIP-induced relaxations are mediated by NO. Spontaneous relaxations of the rat gastroduodenum include responses that involve a GABA ergic NO-related pathway, which is targeted by VIP. In addition, VIP can target NO relaxations of the antrum via other pathways.